STOCKHOLDERS' EQUITY AND NONCONTROLLING INTERESTS - Schedule of Amounts Reclassified Out of Other Comprehensive Earnings (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 30, 2018	Mar. 31, 2017	Mar. 30, 2018	Mar. 31, 2017
Reclassification Adjustment Out Of Accumulated Comprehensive Income [Line Items]
Revenues	$ 729.9	$ 663.2	$ 1,408.4	$ 1,264.7
Net earnings (loss) attributable to Varian	73.2	56.3	(39.1)	70.2
Unrealized loss on defined benefit pension and post-retirement benefit plans
Reclassification Adjustment Out Of Accumulated Comprehensive Income [Line Items]
Cost of revenues & Operating expenses	(0.5)	(1.0)	(0.9)	(1.9)
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment Out Of Accumulated Comprehensive Income [Line Items]
Net earnings (loss) attributable to Varian	(1.5)	(1.0)	(1.8)	(1.9)
Reclassification out of Accumulated Other Comprehensive Income | Unrealized loss on cash flow hedging instruments
Reclassification Adjustment Out Of Accumulated Comprehensive Income [Line Items]
Revenues	$ (1.0)	$ 0.0	$ (0.9)	$ 0.0